Virtual Private Networks (‘VPNs’) are secured private network connections that are built on top of publicly-accessible infrastructure, such as the Internet or the public telephone network. VPNs typically employ a combination of data routers, switches and access controls that allow various types of data to be transmitted between computers.
Typically, VPNs are configured to connect to a service provider's backbone network. Today, service provider networks tend to be Internet protocol (‘IP’) based and are configured to use Multiprotocol Label Switching (‘MPLS’). MPLS is a vendor-independent protocol that applies labels to data packets that are transmitted across a service provider's backbone network.
Effective operation of the network requires that two service Provider Routers (‘P-Routers’) agree on the meaning of labels used to forward traffic between and through them. This common understanding is achieved by a set of procedures, an example being Label Distribution Protocol (‘LDP’), by which one P-Router informs the other of the label bindings it has made. Various MPLS enabled protocols may be used by P-Routers to establish Label Switched Paths (‘LSPs’) through the network by mapping the network-layer routing information directly to the data-link layer switched paths.
Use of VPNs can reduce an organization's networking complexity and costs. For example, rather than setting up and managing individual point-to-point circuits between offices using leased lines, VPN implementations only need to establish one connection from each offices' router (e.g., a Customer Edge Router (‘CE-Router’)) to a service Provider Edge Router (‘PE-Router’). Typically, the PE-Router is linked directly to the service provider's backbone network.
Network monitoring and alarming is critical to understanding the impact of a network fault in the service provider's network. For example, a single network fault in a service provider's backbone network can result in an array of symptoms that impact several VPNs. Associating these symptoms to their original cause can be difficult. A multitude of alarms/traps also may be generated by these symptoms that can cumulatively overwhelm support organizations charged with determining the original cause of network failures. As a result, improved monitoring and alarming techniques to determine the cause of network failures are needed.